Play games
Choose the game that interests you and play itfor free.
Complete the quests
Every game has some quests for which you will receive Soul Gems.
Receive rewards
You can exchange your Soul Gems for Steam Wallet top-ups, game keys, CS:GO Skins and other rewards.
I have a same problem as lala2001, but I stop receiving xp after 4-5 comments and daily maximum is 10 comments.... I am not sure whats happening.